Fifty in the alliance, a fair one (5)

I believe the answer is:

blond

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'a fair one' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?

'fifty in the alliance' is the wordplay.
'fifty' becomes 'L' (Roman numeral).
'in the' means one lot of letters goes inside another.
'alliance' becomes 'bond' (synonyms).
'l' put within 'bond' is 'BLOND'.

Can you help me to learn more?

(Another definition for blond that I've seen is " Fair".)

I've seen this clue in the Sydney Morning Herald.

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